Method for producing polyhydroxyalkanoate and use of same

Abstract

The object of the present invention is to provide a production method which makes it possible to obtain a PHA with a simple operation. The object can be attained by providing a method for producing a polyhydroxyalkanoate, the method including the steps of: (a) preparing an aqueous polyhydroxyalkanoate suspension having a pH of not more than 7; and (b) heating the aqueous polyhydroxyalkanoate suspension, prepared in the step (a), at a temperature set at 80° C. to 300° C. in a twin screw extruder so as to aggregate a polyhydroxyalkanoate.

The invention claimed is: 
     
         1 . A method for producing a polyhydroxyalkanoate, comprising:
 (a) preparing an aqueous polyhydroxyalkanoate suspension having a pH of 7 or less; and   (b) heating the aqueous polyhydroxyalkanoate suspension, prepared in (a), at a temperature set at 80° C. to 300° C. in a twin screw extruder so as to aggregate a polyhydroxyalkanoate,   wherein a pressure in the twin screw extruder is from 0.01 MPa to 0.5 MPa.   
     
     
         2 . The method of  claim 1 , wherein a heating method in (b) is a method in which a heater provided to the twin screw extruder is used and/or a method in which pressurized steam is directly introduced into the twin screw extruder. 
     
     
         3 . The method of  claim 1 , wherein a value expressed by the following Expression (1) is from 50 to 20000:
 a volume median diameter of a polyhydroxyalkanoate aggregate obtained in (b)/a volume median diameter of polyhydroxyalkanoate primary particles ( 1 ).   
     
     
         4 . The method of  claim 1 , wherein, in (a), a concentration of the polyhydroxyalkanoate contained in the aqueous polyhydroxyalkanoate suspension is from 30% by weight to 70% by weight. 
     
     
         5 . The method of  claim 1 , wherein a rotational speed of a screw part of the twin screw extruder is from 30 rpm to 1000 rpm. 
     
     
         6 . The method of  claim 1 , wherein a portion of a screw part of the twin screw extruder has a backward feeding function. 
     
     
         7 . The method for producing a polyhydroxyalkanoate of  claim 1 , wherein a concentration of the polyhydroxyalkanoate contained in the aqueous polyhydroxyalkanoate suspension obtained in (a) is from 40% by weight to 70% by weight. 
     
     
         8 . The method for producing a polyhydroxyalkanoate of  claim 1 , wherein a concentration of the polyhydroxyalkanoate contained in the aqueous polyhydroxyalkanoate suspension obtained in (a) is from 50% by weight to 70% by weight.